1. Field of the Invention
The present invention relates to a method and an apparatus for correcting original image data representing an original image upon printing thereof. The present invention also relates to a computer-readable recording medium storing a program to cause a computer to execute the image correction method.
2. Description of the Related Art
When a user requests photographic printing of image data obtained by a digital camera from a laboratory, the user confirms the content of an image by printing the image data as a proof print with a household printing apparatus such as an ink jet printer. Upon requesting the printing, the image data are provided to the laboratory together with order information for requesting the printing, via a network or by being recorded in a recording medium. In the laboratory, a photographic print of the image data is generated based on the order information. At this time, in order to cause the print to have appropriate color reproducibility, various corrections are carried out on the image data in the laboratory. As methods of carrying out corrections on image data, various methods have been proposed. In one method, RGB color image data are color-converted by using matrix operations so that a print has appropriate color reproducibility (U.S. Pat. No. 5,189,511, for example). In another method, coefficients of a matrix are set in accordance with a characteristic of a printing apparatus as an output device and characteristics of a digital camera and a scanner for obtaining image data so that a print having more preferable color reproducibility can be obtained (U.S. Pat. No. 5,668,596, for example).
However, color reproducibility becomes completely different between prints obtained by using a household printing apparatus and by a printing apparatus in a laboratory, due to differences in color processing methods and coloring characteristics of color materials and/or recording methods employed by these printing apparatus. Therefore, even if the method described in U.S. Pat. No. 5,189,511 or U.S. Pat. No. 5,668,596 is used, color reproducibility does not agree completely between the photographic print and the proof print. As a result, even if the user carries out various kinds of image processing on the image data by using his/her personal computer so as to obtain desirable color reproducibility, the photographic print cannot reflect a result of the image processing, due to the differences in the methods of the color processing and the like.
Meanwhile, a printing apparatus has a color profile describing how colors of input image data appear. Therefore, the laboratory may generate a photographic print having the same color reproducibility as the proof print generated by the household printing apparatus, by referring to the color profile of the printing apparatus provided to the laboratory. In an ink jet printer generally used as a household printing apparatus, the color reproducibility varies, depending on a printing condition such as a standard mode and a high-definition mode. In this case, if color profiles corresponding to all the printing conditions are available, the photographic print having the same color reproducibility as the proof print depending on the printing conditions can be obtained. However, the color profiles corresponding to all the printing conditions are not necessarily available for the household printing apparatus. Furthermore, even if the color profiles are available, specifying a color profile corresponding to an individual printing condition is difficult in some cases. Moreover, formats of the color profiles vary, depending on the printing apparatus. Therefore, the printing apparatus in the laboratory may not read the color profiles of the household printing apparatus.
In the case where the proof print is obtained by correcting colors of image data by using a printer driver, the image data themselves are not subjected to any image processing. Therefore, even if the color profiles are available, the color reproducibility does not agree between the photographic print generated by the laboratory and the proof print.
The proof print may be provided to the laboratory as a color sample. However, causing the color reproducibility of the prints to agree completely is extremely difficult, and an operator of the laboratory may not be skilled enough. If the operator has the skill, the color reproducibility may agree, but productivity decreases.
Meanwhile, if development of a film and generation of first prints of images recorded on the film is requested from a laboratory, a user receives photographic prints for all frames in the film from the laboratory. If the user desires to have an additional print, additional printing of a desired frame is requested. In this case, even in the laboratory that has generated the first prints, colors of the additional print may be different from colors of the corresponding first print, due to changes in printing conditions such as exposure time and a printing environment. In the case where additional printing is requested from a laboratory different from the laboratory that has generated the first prints, the same problem occurs, since printing apparatus generally vary in each laboratory.
Even if the laboratories have identical printing apparatus, or even if the user has the same printing apparatus as in the laboratory, the color reproducibility of the additional print can be different from that of the first print, due to the difference in the printing condition.
Another method of printing using color chart data has also been proposed (Japanese Unexamined Patent Publication No. 7(1995)-254988, for example). In this method, a printing apparatus prints a color chart by using color chart data, and a scanner photoelectrically reads the color chart to generate scanned image data. A table relating data values of the scanned image data and data values of color patches in the color chart is then generated. Meanwhile, the scanner photoelectrically reads a proof print, and image data obtained by the reading are printed after being converted according to the table. By using this method, color reproducibility of a proof print or a first print (hereinafter either of these prints is called a proof print) agrees with a photographic print generated in a laboratory.
However, the method described in Japanese Unexamined Patent Publication No. 7(1995)-254988 contains factors causing image quality degradation, such as defocus and flare of an optical system in a scanner, and degradation and noise of an imaging device upon sampling. Furthermore, a print to be read tends to have a scar and a stain such as fingerprints, and colors degrade due to fading and alteration with time. Therefore, quality of a photographic print generated according to this method becomes lower.